Uni or Partial Knee
Knee arthritis is a common condition, which is initially managed with nonoperative or non-surgical treatment options. These often give people improvement initially, but over time arthritis progresses and eventually for many patients, these will become less effective. Eventually many patients come to a point where they request surgery to help with their pain. This is different for every patient. Arthritis progresses differently for patients, and different patients have different activity levels and daily or work requirements, which will affect people in different ways. When to undergo surgery is a discussion to have with your doctor, and ultimately the decision comes down to you, the patient. Surgery for knee arthritis is an elective surgery, it is not required. It is a decision you as a patient have to be ready for because every surgery will have risks that have to be outweighed by the benefits. You have to be at a point where you are willing to accept those risks because the benefit of surgery and improvement in pain and function are worth it. You also will have rehabilitation that goes along with this, and it will take months of work from you as a patient, while it will only take hours of work from me as your doctor. You have to be ready to put in the work, because you will get out of this what you put into it. A perfectly executed surgery will ultimately have inferior results if appropriate rehab is not performed. And this requires involvement from you as a patient. The best therapist around canʼt do it for you.
Once you have reached the point (physically, mentally, and emotionally) where you are ready to proceed with surgery and the accompanying rehab, surgery for the vast majority of patients comes down to resurfacing or replacement (also called arthroplasty). The two options for the majority of patients are a total knee replacement, where all of the joint surfaces are cut out and replaced with metal and plastic; or a partial knee replacement, where only the diseased or involved portion is resurfaced with metal and plastic, and the remaining intact and healthier areas of the joint are preserved. This decision is also one that should be discussed with your doctor in detail.
Not all patients are candidates for partial knee replacements (also called “uniʼs”, for unicompartmental knee arthroplasty). And not all orthopedic surgeons are fans of partial knee replacements. As with anything, there are pros and cons, or trade-offs for these. Partial knee replacement has had increased interest recently, and is an attractive option for many patients, with some studies suggesting they could be appropriate for up to 15% of patients with knee arthritis.
While total knee replacement is a successful surgery, there are many patients who do not feel like it is a “normal” knee. The goal of this surgery is to improve function and decrease pain, but if there is a way to give you a knee replacement that feels closer to the knee God gave you to start with, then that is an even more attractive option. For many, a partial knee replacement is that option, with many patients and studies showing that a successful partial knee replacement feels and/or functions more closely to a normal knee than a total knee replacement does1. While in the past it was felt that partial knees would only last 8-10 years and should be thought of as a “band-aid”, more recent studies have shown 95% or more of partial knee replacements are still in place at 10 years or more, with some studies showing over 20 years of service from these implants.
Appropriate patient selection is one of the keys to success. Patients with global arthritis in all the areas of their knee are not candidates for partials, they are better served with a total knee replacement. Patients who have primarily one compartment affected (some asymptomatic arthritis changes under the patella might be acceptable) are the ideal candidates for partial knee replacements. However we shouldnʼt just treat your x-rays. Your pain really needs to be localized to the affected compartment. Again, this is a process and decision that needs to be worked through with your treating surgeon.
Another exciting option for partial knee replacement candidates involves how the surgery is performed. This procedure now has the option of being performed with robotic arm-assistance. This procedure is often called a MAKOplasty, named after the Mako robotic arm-assisted surgery option. This procedure uses a CT based 3D reconstruction of your leg and initially became available over a decade ago. It has become increasingly popular in the last 5 years. Studies have shown that partial knee replacements performed with this technology are much more reliable and consistent at placing the implants in the proper position2, which will hopefully show improved longevity and outcomes for patients over time.
While partial knee replacement still can have persistent problems like difficulty kneeling down on the operative knee, they typically are associated with a faster rehabilitation and a more active lifestyle with a knee that is more likely to feel “normal”. The decision on which type of knee replacement to have depends on your knee and the extent of your arthritis and pain, and ultimately comes down to you as a patient based on what your goals are and what you are willing to accept to accomplish those.
- Unicompartmental or total knee replacement: the 15-year results of a prospective randomised controlled trial J Newman, et. al. J Bone Joint Surg [Br] 2009;91-B:52-7.
- Improved Accuracy Of Component Positioning With Robotic-assisted Unicompartmental Knee Arthroplasty. Bell Stuart W., MBChB, MRCP, FRCS(T&O); et. al. The Journal Of Bone And Joint Surgery - Scientific Articles: 20 April 2016 - Volume 98 - Issue 8 - p. 627-635.